Ladders are all too often involved in accidents causing injuries to those using them. There are several different situations in which these accidents occur. Extension ladders have mechanical lock means for keeping the upper section extended but on occasion the mechanical lock is not fully engaged with a rung of the lower section, thereby allowing the upper ladder section to be retracted along the lower section.
Another situation is where the ladder is extended and the upper end is leaning on a wall such that a shifting of weight on the ladder can cause the ladder to slide laterally one direction or the other, causing the ladder to fall.
A third situation is where the upper end of the ladder is placed on a wire such as when cable TV lines are being worked on. The upper end of the ladder can slide along the wire laterally in either direction.
A typical way of stabilizing the ladder when leaning against a wall or wire is to have a person standing on the grounds holding the ladder against undesired movement. This is obviously inefficient and unreliable for preventing ladder accidents.